Music or songs are grouped into collective concepts or categories having common characteristics such as genres and moods. Conventionally, studies have been made on genre identification and mood estimation from musical audio signals. Likewise, singing voices may form a certain category according to the vocal timbre and singing style. For example, when different singers sing the same song or a song in the same musical genre, listeners may recognize differences in singing style (changing vocal timbre, pitch, and power) or may conversely feel that the singing styles of the different singers are similar. If it is possible to explain “how they are similar” in the above-mentioned similarity between the singers, it will help to improve objective understanding of singing voices and facilitate music retrieval and appreciation, and smooth communication. Further, if a certain category can be defined according to the vocal timbre and singing style, studies will be promoted to look into human relationship with music. For example, such category defined according to the vocal timbre and singing style can be utilized as a means of describing the characteristics of singing voices in analyzing the listening impressions on singing voices and the listener's selection of songs in a particular situation or scene.
Studies have been made to characterize or describe singing voices, such as “singer's characteristics” relating to the voice category and gender, “singing style characteristics” relating to fundamental frequency F0 trajectory modeling of vocal segments or singing voices, “listening impressions” relating to the listener's emotions, and “musical characteristics” relating to the musical genres and lyrics.
An invention as disclosed in JP2009-123124A (Patent Document 1), for example, utilizes a part of the above-mentioned characteristics in retrieving unknown songs or music including vocals having similar voice timbres.
In addition to the above-mentioned studies, some techniques have been proposed to analyze latent characteristics of respective vocal sounds as can be known from a plurality of singing voices. Such proposed techniques to analyze latent characteristics of singing voices are listed below (Non-Patent Documents 1 to 7).